The present invention relates to a method of dispensing liquid substances into containers.
The invention finds application to advantage in the field of machines for filling containers both with foamable liquids, typically liquid detergents, sparkling wines and the like, and with viscous fluids such as creamy liquid soaps, gels, oils and similar products: a field to which reference is made specifically in the present specification albeit implying no limitation in scope.
Filling machines of the general type referred to above consist substantially of a tank supported by a main carousel and holding a supply of the liquid substance; the carousel rotates about a vertical axis tangentially to a first transfer station, by way of which it receives a succession of containers each affording a filler mouth.
The tank is rigidly associated with the carousel and affords a plurality of filler valves at the bottom, each of which can be associated with the mouth of a respective container in such a manner that when the carousel is set in motion, the tank rotates about the vertical axis and its contents are dispensed by way of the filler valves into the containers, whereupon the filled containers are directed by way of a second transfer station onto an outfeed conveyor.
Conventionally, when such filling machines are utilized for foamable liquids, it is essential to minimize foaming both when the tank is filled and during the step of dispensing the liquid into each container. Furthermore, it is important to ensure that any foam happening to form and linger inside the tank can be eliminated in as short a time as possible.
With these same ends in view, it has been found advantageous to maintain an appreciable head of the selected substance in the tank, so that the height separating the free surface of the liquid from the outlet of the single filler valve will be as great as possible. In this way the mass of the liquid substance remains inside the tank for a relatively long duration, throughout the operation of filling the containers, and any foam that may have formed during the replenishment of the tank, especially on the surface of the liquid, is allowed a relatively long interval of time in which to dissolve all but completely and in a spontaneous manner before being transferred into the containers.
Conversely, the hydrostatic pressure generated on the bottom of the tank gravitationally by a sizable head of liquid is relatively high, and will produce a high discharge velocity through the outlet of the filler valve.
This high discharge velocity in turn causes the jet of liquid to be dispensed from the filler valve with greater force, occasioning a comparatively violent impact of the jet on the bottom of the respective container, and the formation of foam.
The way to prevent such a situation occurring would be to maintain a relatively small head of the liquid substance inside the tank, though this would contrast with the aforementioned need to promote a spontaneous dissolution of any foam, as a smaller head will shorten the duration for which the liquid remains in the tank and therefore reduce the time available for the foam to dissolve.
It has been found also that in cases where such filling machines are used for dispensing viscous substances, which by reason of their consistency will not flow as readily through the filler valves, a relatively large head needs to be maintained in the tank in such a manner that the mass of fluid bearing gravitationally on the bottom of the tank will generate a hydrostatic pressure sufficient to ensure a discharge pressure at the outlet of each filler valve of which the value is able in turn to ensure a relatively high rate of flow and therefore a suitably fast filling time per single container.
To this end it has been established by experiment that for viscous substances of heavier consistency, such as gels, it can happen that the weight of the head is insufficient to ensure the substance will be forced through the outlets of the filler valves at a reasonably high rate of flow. Accordingly, the expedient by which to obtain bigger heads and thus gravitationally increase the hydrostatic pressure on the bottom of the tank will be to use tanks of significantly greater dimensions and height, which disadvantageously require a lengthy and laborious cleaning operation at the end of the container filling cycle.
Whatever the case, the difficulty associated with making a viscous substance flow smoothly from the filler valves will become more noticeable when the tank begins to empty, as the level of the mass of viscous fluid in the tank subsides gradually to a value at which the gravity-related pressure value of the head is no longer sufficient to ensure that the substance will pass through the outlets of the filler valves at the required rate of flow.
Accordingly, the object of the invention is to provide a method of dispensing liquid substances into containers, such as will ensure that liquids having a relatively low viscosity can be handled without foaming either in the tank or internally of the single containers, and at the same time allow substances of higher viscosity, whatever the type, to be dispensed from the filler valve outlets at an acceptably fast rate of flow throughout the entire duration of the container filling cycle.